What is Tensile Strength? Tensile Strength of Steel and Other Materials

Tensile strength is the maximum stress up to which a material can be loaded without failure. When the tensile strength is exceeded, the material breaks or fails. This is also known as ultimate tensile strength or UTS in abbreviated form. The Tensile Strength of a material is a very important parameter in mechanical design as all components are designed in such a way that the generated stress in that part does not exceed tensile strength during the design life of the component. In this article, we will discuss more regarding Tensile Strength, its definition, its significance, measuring methods, and typical values.

Definition of Tensile Strength

Mathematically, the tensile strength of a material is defined as the ratio of the maximum load that the material can support to its original cross-sectional area. So, UTS=Maximum force to create failure of the body/Cross-Sectional Area=F/A.

From the above equation, it is evident that the unit of Tensile strength is N/m2 or Pa (pascal) in SI systems. In the FPS system, the unit of tensile strength is psi or lb/in2. Usually, the tensile strength of materials is expressed in MPa or psi.

In the stress-strain curve of a material, it is the maximum stress value before failure as shown in Fig. 1 (Image Credit: https://mechanicalc.com/reference/mechanical-properties-of-materials) below.

Tensile Strength in Stress-Strain Curve
Fig. 1: Tensile Strength in Stress-Strain Curve

Significance of Tensile Strength

Tensile strength is the maximum stress generated before fracture. So, it can be stated as for a given cross-section, the maximum load that the material can be subjected to can be easily calculated. This maximum load or stress value is very important. Tensile Strength data is required for various purposes as mentioned below:

  • Structural and Mechanical Design
  • Material Evaluation
  • Preparing Material Specification
  • Quality Control
  • Failure Analysis
  • Modeling to predict material behavior under complex loading conditions.
READ  Flexible Metal Hoses: An essential guide

The tensile strength is the material’s resistance to tension. The more the tensile strength of a part, the more difficult it is to stretch, and more force is required to stretch it.

Factors Affecting Tensile Strength

Tensile Strength is an intensive property of a material and independent of the size of the specimen. The value of tensile strength varies from one material to the other. The factors that affect the tensile strength in metals are:

  • Temperature: With an increase in the temperature of a material the tensile strength decreases.
  • Surface Defects: Specimens with defects have less tensile strength as compared to materials without defects.
  • Specimen Preparation: Tensile strength of a material depends on the surface preparation of the materials. This is the reason that a standard philosophy as outlined in Codes and Standards is followed for specimen preparation.
  • Heat Treatment: Heat treatment can modify the tensile strength of metals.
  • Amount of Cold Work on the material

Measuring Tensile Strength

Tensile strength measures a material’s resistance to breaking. The tensile test for metals is measured by performing tensile testing in a universal testing machine. Various ASTM codes provide guidelines for the tensile testing procedure. For example, ASTM E8 provides standard test methods for metallic materials and ASTM D638 provides tensile testing procedures for plastic materials.

READ  Underwater Welding & Inspection Overview

A universal testing machine has two crossheads where the specimen is fitted and an increasing tensile load is applied to extend the specimen till it breaks. the elongation against the applied force is plotted automatically by the instrument from which the stress-strain curve is generated. The tensile strength is decided from that curve (Refer to Fig. 1) as the maximum stress point in the curve during failure.

Common codes and standards that are followed for tensile testing are ASTM E8/E8M, ISO 6891, JIS Z2241, ASTM D3039, ASTM D638, ASTM D828, ASTM D882, ISO 37, MPIF Test Standard 10, etc.

The tensile strength of a material can be measured by the above-mentioned process. But Scientists in research organizations have already standardized tensile strength values for all common materials in various codes and standards like ASME BPVC codes, ASME B codes, etc. So, Engineers need to simply follow the relevant code and standard and find out the tensile strength of the material from standardized tables provided in those codes.

Tensile Strength vs Yield Strength

Yield Strength is the property of ductile materials. For brittle materials, distinct yield strength is not obtained. Hence, proof stress is determined by drawing a parallel line to the straight elastic region of the stress-strain curve starting from 0.2% of strain. The main differences between Tensile Strength and Yield Strength are tabulated below:

READ  What is HDPE Pipe? | Types and Design of HDPE Pipes
Tensile StrengthYield Strength
Tensile strength is measured at the point of fracture.Yield Strength is measured at the point of plastic deformation.
Tensile strength is a design parameter for brittle materials.Yield strength is the design parameter for ductile materials.
The value of tensile strength is always higher than yield strength.The value of Yield Strength is lower than tensile strength.
After tensile strength, the material fails.After Yield Strength, the material loses its elastic behavior.
Table 1: Tensile Strength vs Yield Strength

Tensile Strength of Steel

The tensile strength of steel provides the value of tensile stress that a steel component can withstand until it leads to failure in any of two ways: ductile or brittle failure. Click here to know more about ductile and brittle failure.
The tensile strength of common steels for industrial use is provided in the following table (Table 2):

Steel MaterialTensile Strength (MPa)Yield Strength (MPa)Tensile Strength (ksi)Yield Strength (ksi)
Structural Steel, ASTM A36400-55025058-8036
Mild Steel, 109084124712236
Maraging Steel, 280026932617391380
Chromium Vanadium Steel94062013690
API 5L X655314487765
ASTM A514760690110100
Chromium-Nickel Austenitic Stainless Steel520-72021075-10430
Molybdenum Chromium Nickel Austenitic Stainless Steel520-67022075-9732
Duplex Steels640-85046093-12367
Stainless Steel AISI 30286050212573
Ferritic Stainless Steel5002807341
Martensitic Stainless Steel6503509451
Precipitation Hardening Stainless Steel11001000160145
Ordinary Carbon Steel315-610195-27546-8828-40
Tool Steel-Annealed280-700180-36041-10226-52
Tool Steel-Normalised530-760380-43077-11055-62
Tool Steel-Cold Hardened750-1200109-174
Alloy Structural Steel500-75073-109
API 5L X424142906042
API 5L X524553596652
API 5L X605174147560
A106 B4142416035
API 5L B4142416035
Table 2: Tensile and Yield Strength of Steel

Tensile Strength of Other Materials

The following table (Table 3) provides the tensile strength of some common materials.

MaterialTensile Strength (MPa)Yield Strength (MPa)
Cast Iron, ASTM A48200130
ABS plastics40 
A53 Seamless and Welded Standard Steel Pipe – Grade A331207
A53 Seamless and Welded Standard Steel Pipe – Grade B414241
A106 Seamless Carbon Steel Pipe – Grade A400248
A106 Seamless Carbon Steel Pipe – Grade C483276
A252 Piling Steel Pipe – Grade 1345207
A252 Piling Steel Pipe – Grade 2414241
A252 Piling Steel Pipe – Grade 3455310
A501 Hot Formed Carbon Steel Structural Tubing – Grade A400248
A501 Hot Formed Carbon Steel Structural Tubing – Grade B483345
A523 Cable Circuit Steel Piping – Grade A331207
A523 Cable Circuit Steel Piping – Grade B414241
A618 Hot-Formed High-Strength Low-Alloy Structural Tubing – Grade Ia & Ib483345
A618 Hot-Formed High-Strength Low-Alloy Structural Tubing – Grade II414345
A618 Hot-Formed High-Strength Low-Alloy Structural Tubing – Grade III448345
API 5L Line Pipe310 – 1145175 – 1048
Boron 3100
Cast Iron 4.5% C, ASTM A-48170 
Cellulose,  cotton, wood pulp, and regenerated80 – 240 
Cellulose acetate, sheet30 – 52 
Cellulose nitrate, celluloid50 
Chlorinated polyether39 
Concrete, High Strength (compression)40 
Douglas fir Wood50 
Epoxy resins26 – 85 
Nylon-645 – 9045
Nylon-6660 – 80 
Phenolic cast resins33 – 59 
Phenol-formaldehyde molding compounds45 – 52 
Pine Wood (along the grain)40 
Polyacrylonitrile, fibers200 
Polycarbonates52 – 62 
Polyethylene HDPE (high density)15 
Polyethylene Terephthalate, PET55 
Polyisoprene, hard rubber39 
Polyimide aromatics68 
Polypropylene, PP28 – 36 
Polystyrene, PS30 – 100 
Polyurethane cast liquidOct-20 
Polyurethane elastomer29  – 55 
Silicon Carbide 3440
Steel, High Strength Alloy ASTM A-514760690
Steel, stainless AISI 302860502
Steel, Structural ASTM-A36400250
Titanium Alloy900730
Table 3: Tensile Strength of materials

Anup Kumar Dey

I am a Mechanical Engineer turned into a Piping Engineer. Currently, I work in a reputed MNC as a Senior Piping Stress Engineer. I am very much passionate about blogging and always tried to do unique things. This website is my first venture into the world of blogging with the aim of connecting with other piping engineers around the world.

2 thoughts on “What is Tensile Strength? Tensile Strength of Steel and Other Materials

  1. Can you please elaborate
    1. whether and when we should use tensile or yield strength for calculating thickness of vessel or pipe.
    2. Since there is a range of values of tensile strength shall we use lower value to calculate thickness
    3. From where we can get variation in value of tensile and yield strength with temperature.

  2. What is the tinsel strength of api5l 36” X70 625 wall ERW pipe.
    When pulling a bore what is the maximum amount of pounds you can put on it
    When you pull back the bore pipe

Leave a Reply

Your email address will not be published. Required fields are marked *

Recent Posts