CN114252334B - A method for testing the creep properties of high modulus polyethylene ropes - Google Patents

Abstract

A method for testing the creep performance of high modulus polyethylene ropes belongs to the field of polymer fiber rope performance testing. Under normal temperature conditions, a testing machine with a pin fixed to a rope sample and an eye ring is used to test the creep performance of the rope; the stretching, pausing, and reciprocating cyclic motion of the testing machine pin are used to eliminate the structural elongation of the rope; after the rope sample is tensed for a period of time under a preselected tension T, the displacement of two marks in the middle of the rope sample is used to calculate the creep elongation, creep rate and specific stress value of the rope; the spacing between the two pins of the testing machine with a pin fixed to the eye ring sample is not less than 1800mm; the tension T is selected to be 50% to 20% of the rope breaking strength, and its deviation range is 0.1 to 1%; the spacing between the two marks is not less than 1000mm; the creep elongation, creep rate and specific stress of the creep performance of the high modulus polyethylene rope are measured under constant load. It can be used to establish a model of creep performance of high modulus polyethylene ropes with different breaking strengths and various linear densities.

Description

A method for testing the creep properties of high modulus polyethylene ropes

Technical Field

The invention belongs to the field of polymer fiber rope performance detection, and in particular relates to a method for testing the load creep performance of a high modulus polyethylene rope.

Background Art

High modulus polyethylene fiber is the third generation of high-performance fiber after carbon fiber and aramid. The rope made of it has the highest breaking strength, which is 8 times that of steel wire rope. When the breaking strength is the same, the required diameter is the thinnest, which is 50% of that of polypropylene rope. When the diameter is the same, its breaking strength is the largest, which is 3.8 times that of polypropylene rope. Its fatigue strength is extremely high, and the strength retention rate after accelerated fatigue test is >100%.

The high performance of high modulus polyethylene fiber determines its increasing application in mooring cables in offshore platform anchor cable positioning systems. High modulus polyethylene mooring cables (also known as high modulus polyethylene ropes) have developed into one of the key supporting high-end equipment for the development of offshore oil and gas resources.

Creep refers to the phenomenon of plastic deformation that occurs slowly and continuously over time under a certain temperature and constant stress.

Due to the long molecular chain and small intermolecular force, high modulus polyethylene fiber will produce molecular chain slippage under long-term constant load, that is, irreversible deformation-creep. This phenomenon strongly depends on load, time and temperature.

High modulus polyethylene mooring cables work for a long time under constant load, and their creep performance is related to the safety of offshore platforms. Therefore, when high modulus polyethylene fibers are used as mooring cables for offshore platforms, a corresponding creep performance document model must be established.

The Chinese invention patent with the authorization announcement number CN 103234841 B and the authorization announcement date of February 10, 2016 discloses a method for testing the tensile creep properties of ultra-high molecular weight polyethylene fibers, which uses a fiber tensile testing machine at room temperature with creep load, tensile speed, creep time, and fiber test length as independent variables to measure the creep elongation of the fiber. The method is to clamp the two ends of the fiber sample into the upper and lower clamps respectively, gradually apply the load at a set tensile speed, maintain a certain creep time from the initial load to the creep load, and the recorded sample elongation is the creep elongation. The creep time of this method is 10 to 100 minutes and the test length is 100 to 500 mm, which does not meet the requirements of the creep performance test of high modulus polyethylene ropes, which requires a creep time in hours and a minimum effective length of 1800 mm. This method uses the distance between the upper and lower clamps of the fiber tensile tester as the test length of the specimen, and calculates the elongation from the displacement value of the clamp. Since high modulus polyethylene fibers are prone to slide out of the clamp part of the length during the test, the elongation test will be biased. The constant load elongation described in this method is the elongation of the fiber during the creep time after reaching the creep load. Although the elongation remains unchanged after the tester stops stretching during the creep time, the tensile stress on the fiber decreases with time. Therefore, the elongation of the stretch is measured, not the creep elongation under constant load.

The standard GB/T30668-2014 for high modulus polyethylene (UHMWPE) ropes, "UHMWPE fiber 8-strand, 12-strand braided ropes and double braided ropes", specifies the requirements for the linear density and breaking strength of physical properties, which are measured under the test methods and test conditions specified in GB/T 8834 "Determination of physical and mechanical properties of ropes". GB/T30668 does not have requirements for rope elongation and creep properties, but also points out that "different grades of UHMWPE filaments should pay attention to different creep properties".

The standard GB/T 8834 "Determination of Physical and Mechanical Properties of Ropes" for fiber rope testing methods specifies the test methods for rope linear density, lay length, elongation, and breaking strength, but does not include the test method for rope creep performance. The steps for measuring rope elongation are: measure the distance between the two marks in the middle of the sample under pre-tension; gradually increase the tension by stretching at a uniform speed through the reciprocating parts of the testing machine, stop the machine when the tension reaches 75% of the breaking strength, measure the distance between the two marks as soon as possible, and calculate the rope elongation from the two gauge lengths before and after stretching. This method determines the tensile stress of the rope as time goes on after the stretching stops, so it measures the elongation of the stretching, not the creep elongation under constant load.

How to correctly measure the constant load creep parameters and related properties of high modulus polyethylene fibers is a key technical problem that needs to be solved urgently in actual measurement work.

Summary of the invention

In order to overcome the defect of the prior art that the tensile elongation is measured instead of the constant load creep elongation, the technical solution of the present invention provides a method for testing the creep performance of high modulus polyethylene ropes. The implementation of the technical solution can establish a document model of the creep performance of high modulus polyethylene ropes with different breaking strengths and various linear densities; from this model, creep performance data (creep rate, allowable creep elongation and time) can be obtained, and the annual creep expectation and the cumulative creep elongation of the entire rope design life can be predicted. The comparison under the same specific stress and temperature conditions can know the ratio of the rope creep rate to the fiber creep.

The technical solution of the present invention is to provide a method for testing the creep performance of a high modulus polyethylene rope, wherein the tested creep performance of the rope at least includes the creep elongation of the rope, the creep rate of the rope and the specific stress of the rope; the method is characterized in that the method for testing the creep performance of the high modulus polyethylene rope is carried out under the following modes and conditions:

Under normal temperature conditions, the testing machine with a pin fixing the rope sample and inserting the eye ring is used to test the creep performance of the rope;

The stretching, pausing, and reciprocating motion of the testing machine pin are used to eliminate the structural elongation of the rope;

After the rope sample is subjected to the preselected tension T for a period of time, the displacement of the two marks in the middle of the rope sample is used to calculate the creep elongation, creep rate and specific stress value of the rope;

The creep test of the rope shall be carried out under temperature control, with the temperature not exceeding 25°C and the temperature difference within 5°C;

The distance between the two pins of the eye ring specimen testing machine fixed with pins shall not be less than 1800mm;

The tension T is selected to be 50% to 20% of the rope breaking strength, with a deviation range of 0.1 to 1%;

The distance between two marks shall not be less than 1000mm;

The method for testing the creep performance of the high modulus polyethylene rope is to measure the creep elongation, creep rate and specific stress of the creep performance of the high modulus polyethylene rope under a constant load.

The method for testing the creep performance of a high modulus polyethylene rope is used to establish a document model of the creep performance of high modulus polyethylene ropes with different breaking strengths and various linear densities; from this model, the creep data of the rope sample can be obtained, the annual creep expectation and the cumulative creep elongation of the entire rope design life can be predicted, and the ratio of the rope creep rate to the fiber creep of the rope sample can be obtained by comparison under the same specific specific stress and temperature conditions.

Specifically, the creep data at least includes creep rate, allowable creep elongation and time.

Furthermore, the method for testing the creep performance of high modulus polyethylene rope comprises the following steps:

Step 1: Install the specimen in the testing machine;

Step 2: Apply a load equal to 2% of the rope’s breaking strength;

Step 3: The extensometer should be installed between the two marks on the rope;

Step 4: The tension is increased at a rate of 10% of the rope's breaking strength per minute to 50% of the rope's breaking strength and then maintained for 30 minutes;

Step 5: The tension is reduced at a rate of 10% of the rope breaking strength per minute to 20% of the rope breaking strength;

Step 6: The tension is cycled 300 times between 10% and 30% of the rope breaking strength at a frequency of 0.03 Hz to 0.1 Hz;

Step 7: The sample must be kept at the predetermined controlled temperature and pre-selected tension T for at least 7 days. The gauge length should be measured continuously during this time, with a sampling rate of at least once per hour.

Step 8: The sample is unloaded.

Furthermore, the method for measuring and calculating the creep performance of the high modulus polyethylene rope includes:

The following three gauge lengths are measured:

5.1) In steps 3–5, measure the gauge length of the tensile load;

5.2) In step 6, measure the gauge length of the cyclic load;

5.3) In step 7, preselect the gauge length and completion time under tension T;

Specifically, in step 7, the sampling rate of the continuous measurement is at least once per hour.

Furthermore, the creep performance of the tested cable is calculated using the following formula:

A. Creep elongation:

G = [(ll ₂ )/l ₂ ] × 100%

Where:

G is creep elongation, %; l is the gauge length under the preselected tension T in step 7, in millimeters; _l2 is the gauge length at the breaking strength of 2% in step 2, in millimeters;

B. Creep rate:

_Gt ＝G/h

Where: _Gt is the creep rate, ﹪/h; G is the creep elongation, ﹪; h is the creep time, in hours;

C. Specific stress:

S _C =T/ρ

Where: Sc is the specific stress of the rope, in Newton/tex; T is the tension preselected in step 7, in kilonewtons; ρ is the linear density of the rope, in kilotex.

Furthermore, the method for testing the creep performance of high modulus polyethylene rope comprises the following contents or steps:

8.1) Temperature control;

8.2) Sample preparation and initial measurement;

8.3) Testing machine control;

8.4) Experimental preparation;

8.5) Creep performance test;

8.6) Calculation of rope creep properties;

8.7) Record the data that should be recorded.

Further, in the method for testing the creep properties of high modulus polyethylene rope:

A. The temperature control includes controlling the temperature of the test chamber so that the temperature does not exceed 25°C and the temperature difference is within 5°C;

B. The sample preparation and initial measurement include cutting a sample of 2 meters of rope plus 10 lay lengths, measuring the initial length L ₀ and weighing the mass m, making two r marks with a spacing of not less than 1 meter in the middle, and measuring the initial gauge length l ₀ ;

C. The control of the testing machine includes a testing machine that uses a pin to fix the rope sample and insert the eye ring, and the distance between the two pins is not less than 1800mm; wherein, the stretching speed of the testing machine; before the pre-selected tension T is tightened on the sample, it is a normal speed level, and the motor speed is adjusted to meet the requirements of the loading rate; when the pre-selected tension T is tightened on the sample, it is a low speed level, and the motor speed adjustment is slow or stopped to make the pre-selected tension T fluctuate within the range of 0.1 to 1% to achieve the effect of load stability;

D. The test preparation includes:

D1) The specimen is installed on the testing machine;

D2) The extensometer should be installed between the rope marks and the camera focus and aperture should be adjusted;

D3) Apply a load of 2% of the rope breaking strength and measure the gauge length l ₂ ;

E. The creep performance test includes:

E1) Eliminate the structural elongation of the rope;

E2) Determination of steady-state creep under constant tension;

E3) The sample should be unloaded after the test.

In the technical solution of the present invention, the creep elongation of the rope is the plastic elongation that increases slowly and continuously with time under a certain temperature and constant tension; the creep rate of the rope is the creep elongation per unit time; and the specific stress of the rope is the tension per unit linear density.

Compared with the prior art, the advantages of the present invention are:

1. The method for testing the creep performance of high modulus polyethylene rope provided by the technical solution of the present invention overcomes the defects of the prior art that a constant load cannot be applied to the rope due to a high tensile speed, and what is measured is the tensile elongation rather than the creep elongation under a constant load;

2. The technical solution of the present invention is to measure the creep elongation, creep rate and specific stress of the creep properties of high modulus polyethylene rope under constant load;

3. The implementation of the technical solution of the present invention can establish a document model of the creep performance of high modulus polyethylene ropes with different breaking strengths and various linear densities; from this model, creep data (creep rate, allowable creep elongation and time) can be obtained, and the annual creep expectation and the cumulative creep elongation of the entire rope design life can be predicted. By comparing under the same specific specific stress and temperature conditions, the ratio of the rope creep rate to the fiber creep of the rope sample can be obtained.

DETAILED DESCRIPTION

The present invention is further described below.

The creep properties of the rope tested by the present invention include the creep elongation of the rope - the plastic elongation that increases slowly and continuously with time under a certain temperature and constant tension; the creep rate of the rope - the creep elongation per unit time; and the specific stress of the rope - the tension per unit linear density.

The technical solution of the present invention realizes the test of the creep performance of the rope by the following methods:

The testing machine, which uses pins to fix rope specimens and insert eyelets under normal temperature conditions, is used to test the creep performance of ropes.

The stretching, pausing, and reciprocating motion of the testing machine pin are used to eliminate the structural elongation of the rope;

After the rope sample is subjected to the preselected tension T for a period of time, the displacement of the two marks in the middle of the rope sample is used to calculate the creep elongation, creep rate and specific stress value of the rope.

The creep test of the rope in this technical solution should be carried out under temperature controlled conditions, with the temperature not exceeding 25°C and the temperature difference within 5°C.

The distance between the two pins of the eye ring specimen testing machine fixed with pins shall not be less than 1800mm.

The tension T should be selected to be 50% to 20% of the rope breaking strength, with a deviation range of 0.1 to 1%.

The distance between two marks shall not be less than 1000mm.

The present invention also provides a method for testing the creep performance of a high modulus polyethylene rope, comprising the following steps:

Step 1: Install the specimen in the testing machine;

Step 2: Apply a load equal to 2% of the rope’s breaking strength;

Step 3: The extensometer should be installed between the two marks on the rope;

Step 4: The tension is increased at a rate of 10% of the rope's breaking strength per minute to 50% of the rope's breaking strength and then maintained for 30 minutes;

Step 5: The tension is reduced at a rate of 10% of the rope breaking strength per minute to 20% of the rope breaking strength;

Step 6: The tension is cycled 300 times between 10% and 30% of the rope breaking strength at a frequency of 0.03 Hz to 0.1 Hz;

Step 7: The sample must be kept at the predetermined controlled temperature and pre-selected tension T for at least 7 days. The gauge length should be measured continuously during this time, with a sampling rate of at least once per hour.

Step 8: The sample should be unloaded.

The present invention also provides a method for measuring and calculating the creep performance of high modulus polyethylene ropes:

The following three gauge lengths are measured:

1) Steps 3-5, gauge length of tensile load;

2) Step 6, gauge length of cyclic load;

3) Step 7, pre-select the gauge length and completion time under tension T (continuous measurement sampling rate: minimum once per hour).

The creep performance of the tested rope is calculated using the following formula:

A. Creep elongation:

G = [(ll ₂ )/l ₂ ] × 100%

Where:

G—creep elongation, %;

l—the gauge length under the preselected tension T in step 7, in millimeters (mm);

l ₂ — gauge length when the breaking strength is 2﹪ in step 2, in millimeters (m).

B. Creep rate:

_Gt ＝G/h

Where:

_Gt — creep rate, ﹪/h;

G—creep elongation, ﹪;

h—creep time, in hours (h).

C. Specific stress:

S _C =T/ρ

Where:

Sc—specific stress of the rope, in Newton/tex (N/tex);

T—the tension preselected in step 7, in kilonewtons (kN);

ρ—Linear density of the rope, in ktex.

Best Practice:

1. Temperature control:

Control the test room temperature so that it does not exceed 25°C and the temperature difference is within 5°C; record the temperature during the creep test;

2. Sample preparation and initial measurement:

Cut a sample of 2 meters plus 10 lay lengths of rope, measure the initial length L ₀ (accurate to 0.5%) and weigh the mass m (accurate to 0.5%), make two r marks with a spacing of not less than 1 meter in the middle, and measure the initial gauge length l ₀ (accurate to 0.5%);

3. Testing machine control:

The testing machine adopts pins to fix the rope specimen and insert the eye ring. The distance between the two pins is not less than 1800mm. Among them, the tensile speed of the testing machine is normal speed before the pre-selected tension T is applied to the specimen, and the motor speed is adjusted to meet the requirements of the loading rate. When the pre-selected tension T is applied to the specimen, it is low speed. The slow speed or stop of the motor speed adjustment makes the pre-selected tension T fluctuate within the range of 0.1～1﹪, which can achieve the effect of load stability.

4. Test preparation:

1) The sample is installed on the testing machine;

2) The extensometer should be installed between the rope marks and the camera focus and aperture should be adjusted;

3) Apply a load of 2% of the rope breaking strength and measure the gauge length l ₂ (accurate to 0.5%);

5. Creep performance test:

1) Eliminate the structural elongation of the rope;

The stretching, pausing, and reciprocating motion of the testing machine pin are used to eliminate the structural elongation of the rope:

a) The tension is applied at a rate of 10% of the rope's breaking strength per minute to 50% of the rope's breaking strength and then maintained for 30 minutes;

b) The tension is reduced at a rate of 10% of the rope breaking strength per minute to 20% of the rope breaking strength;

c) The tension is cycled 300 times at a frequency of 0.03 Hz to 0.1 Hz between 10% and 30% of the rope breaking strength;

2) Determination of steady-state creep under constant tension:

The constant tension T is 50% to 20% of the rope breaking strength; it must be at a predetermined controlled temperature and pre-selected tension T for at least 7 days, during which the gauge length l should be measured continuously (accurate to 0.5%), with a sampling rate of at least once per hour;

3) The sample should be unloaded after the test;

6. Calculation of rope creep performance:

1) Linear density:

ρ＝m/L ₁

L ₁ = l ₂ × L ₀ / l ₀

Where:

ρ—rope linear density, in ktex;

m—mass of the sample, in grams (g);

L ₁ — length of the sample when the breaking strength is 2% tension, in meters (m);

l ₂ — gauge length when the breaking strength is 2%, in meters (m);

L ₀ —initial length, in meters (m);

l ₀ —initial scale length, in meters (m).

2) Creep elongation:

G = [(ll ₂ )/l ₂ ] × 100

Where:

G—creep elongation, %;

l—gauge length under pre-selected tension T, in millimeters (mm);

l ₂ — gauge length when the breaking strength is 2%, in millimeters (m).

3) Creep rate:

_Gt ＝G/h

Where:

_Gt — creep rate, ﹪/h;

G—creep elongation, ﹪;

h—creep time, in hours (h).

4) Specific stress:

S _C =T/ρ

T＝t×F _MBS

Where:

Sc—specific stress of the rope, in Newton/tex (N/tex);

T—preselected tension, in kilonewtons (kN);

ρ—linear density of the rope, in ktex;

t—stress ratio, ﹪;

F _MBS — Specific minimum rope breaking strength in Newtons (N).

7. The following data should be recorded:

— Sample type and linear density;

—stress ratio τ and specific stress Sc;

— temperature during creep testing;

—Creep elongation and creep rate.

The technical solution of the present invention measures the creep elongation, creep rate and specific stress of the creep performance of a high modulus polyethylene rope under constant load conditions; by adopting the technical solution of the present invention, a document model of the creep performance of high modulus polyethylene ropes with different breaking strengths and various linear densities can be established; from this model, creep data (creep rate, allowable creep elongation and time) can be obtained, and the annual creep expectation and the cumulative creep elongation of the entire rope design life can be predicted. By comparison under the same specific specific stress and temperature conditions, the ratio of the rope creep rate to the fiber creep can be obtained.

The invention can be widely used in the field of constant load creep test of high modulus polyethylene fibers.

Claims (6)

1. A method of testing the creep performance of a high modulus polyethylene rope, the tested rope creep performance comprising at least rope creep elongation, rope creep rate and rope specific stress; the method is characterized in that the method for testing the creep property of the high-modulus polyethylene rope is carried out under the following modes and conditions:

Under the normal temperature condition, the testing machine for fixing the rope sample by the pin column and inserting the eye ring is used for testing the creep performance of the rope; the tensile, pause and reciprocating cyclic motion of the pin of the tester is used for eliminating the structural elongation of the rope, and comprises the following steps:

step 1: applying a load of 2% of the rope breaking strength;

step 2: the extensometer is arranged between the two marks of the rope;

Step 3: the tension is maintained for 30 minutes after loading the speed of 10% of the rope breaking strength to 50% of the rope breaking strength;

Step 4: the tension is reduced by 10% of the rope breaking strength per minute to 20% of the rope breaking strength;

Step 5: the tension circulates 300 times between 10% and 30% of the rope breaking strength at a frequency of 0.03 hz to 0.1 hz;

Step 6: at least 7 days under tension of a preselected tension T at a predetermined control temperature, the gauge length should be measured continuously at this time, with the sampling rate being at least once per hour;

After the pre-selected tension T is tensed for a period of time, the creep elongation, creep rate and specific stress value of the rope are calculated by the displacement of the two marks in the middle of the rope sample;

The rope creep test is carried out under the condition of controlling the temperature, the temperature is not more than 25 ℃ and the temperature difference is within the range of 5 ℃;

The distance between two pins of the pin fixing plug-in eye ring sample testing machine is not less than 1800mm;

The tension T is 50 to 20 percent of the breaking strength of the rope, and the deviation range is 0.1 to 1 percent;

the distance between the two marks is not less than 1000mm;

the method for testing the creep performance of the high-modulus polyethylene rope comprises the steps of measuring the creep elongation, the creep rate and the specific stress of the creep performance of the high-modulus polyethylene rope under constant load;

the creep performance of the cable to be tested is calculated by using the following formula:

A. creep elongation:

G＝[(l-l₂)/l₂]×100％

Wherein:

G is creep elongation,%; l is the gauge length under the pre-selected tension T tension in the step 6, and the unit is millimeter; l ₂ is the gauge length in millimeters when breaking the strength 2% in the step 1;

B. Creep rate:

G_t＝G/h

Wherein: g _t is creep rate,%/h; g is creep elongation; h is creep time in hours;

C. specific stress:

S_C＝T/ρ

Wherein: sc is the specific stress of the rope in Newton/tex; t is a preselected tension in kilonewtons; ρ is the linear density of the rope in kilo [ tex ].

2. The method for testing the creep property of the high-modulus polyethylene rope according to claim 1, wherein the method for testing the creep property of the high-modulus polyethylene rope is used for establishing a document model of the creep property of the high-modulus polyethylene rope with different breaking strength and various linear densities; from this model, creep data of the rope sample can be obtained, creep expectation per year, cumulative creep elongation of the whole rope design life can be predicted, and the ratio of the rope creep rate to the fiber creep of the rope sample can be obtained by comparison under the same specific stress and temperature conditions.

3. The method of testing the creep properties of a high modulus polyethylene rope according to claim 2, wherein said creep data comprises at least creep rate, allowable creep elongation and time.

4. The method for testing creep properties of a high modulus polyethylene rope according to claim 1, wherein said method for measuring and calculating creep properties of a high modulus polyethylene rope comprises:

the following 3 gauge lengths were measured:

4.1 Step 2-4), measuring the gauge length of the tensile load;

4.2 In step 5), measuring the gauge length of the cyclic load;

4.3 In step 6), the gauge length and the completion time under tension T are preselected.

5. The method for testing creep properties of a high modulus polyethylene rope according to claim 1, wherein said method for testing creep properties of a high modulus polyethylene rope comprises the following contents or steps:

5.1 Temperature control;

5.2 Sample preparation and initial measurement;

5.3 A testing machine regulates and controls;

5.4 Test preparation;

5.5 Creep performance test;

5.6 Calculation of the creep properties of the rope;

5.7 Record the data that should be recorded.

6. The method for testing creep properties of a high modulus polyethylene rope according to claim 5, wherein

A. The temperature control comprises controlling the temperature of a laboratory to ensure that the temperature is not more than 25 ℃ and the temperature difference is within the range of 5 ℃;

B. The sample preparation and initial measurement comprises the steps of intercepting a sample with the length of 2 meters and 10 lay lengths of a rope, measuring the initial length L ₀ and the weighing mass m, marking two r marks with the distance of not less than 1 meter at the middle part, and measuring the initial gauge length L ₀;

C. the regulation and control of the testing machine comprise a testing machine for fixing rope samples to be inserted into eye rings by adopting pins, wherein the distance between the two pins is not less than 1800mm; wherein, the stretching speed of the tester; the speed is regulated by a motor to meet the requirement of loading speed when the preselected tension T is constant before tensioning the sample; when the preselected tension T is in tension on the sample, the speed is low, and the preselected tension T fluctuates within the 0.1-1% range due to the micro speed or the shutdown of the motor speed regulation so as to achieve the effect of constant load;

D. the test preparation comprises:

d1 A test sample is arranged on a testing machine;

D2 An extensometer is arranged between the rope marks, and the focal length and the aperture of the camera are adjusted;

d3 2% of the rope breaking strength is applied, and the gauge length l ₂ is measured;

E. the creep performance test comprises the following steps:

e1 Eliminating structural elongation of the rope;

E2 Measuring steady state creep at constant tension;

E3 The sample should be unloaded after the test is completed.