DEBRE BERHAN UNIVERSITY
College Of Engineering
Department Of Mechanical Engineering
Strength of Materials I
Module
Dejenie W.
Date april/2026
,Strength of Materials I [DATE]
1. Introduction
Branch of mechanics that deals with behavior of materials subjected to various type of
loadings is called Mechanics of solids/mechanics of material or Mechanics of deformable
bodies.
Strength of materials is one branch of mechanics of material;
It deals with the relations between the external forces applied to elastic bodies
and the resulting deformations and stresses.
In the design of structures and machines, the application of the principles of
strength of materials is necessary.
Forces are produced by the action of gravity, by accelerations and impacts of
moving parts, by gasses and fluids under pressure, by the transmission of
mechanical power, etc.
In order to analyze the stresses and deflections of a body, the magnitudes,
directions and points of application of forces acting on the body must be known.
1.1. Types of Loads in Mechanics of Materials
In mechanics of materials, a load is any external force or moment applied to a body that
causes stress, deformation, or failure. Based on how the force acts on the material, loads
are commonly classified as follows:
Axial Load
The Load is applied along the axis of a member. It can be tensile or compressive.
a. Tensile Load
Acts away from the material, trying to stretch it.
Produces tensile stress and elongation.
Common in tie rods, cables, suspension bridges.
b. Compressive Load
Acts towards the material, trying to shorten or crush it.
Produces compressive stress.
Common in columns, pillars, foundations.
pg. 1 DBU
, Strength of Materials I [DATE]
Shear Load
Forces act parallel to the cross-section of the material.
Tends to cause one part of the material to slide over another.
Produces shear stress.
Transverse Load
Applied perpendicular to the longitudinal axis of a member.
Causes the member to bend.
One side experiences tension, the opposite side compression.
Torsional Load
Twisting action caused by a pair of externally applied
equal and oppositely directed couples acting in parallel planes.
Causes the member to twist about its longitudinal axis.
Produces shear stress due to torque.
Distributed Load
Load spread over a length, area, or volume.
Uniformly Distributed Load (UDL) and Uniformly Varying Load (UVL) are
common types of distributed loads.
Impact Load
The impact could be caused by a weight falling on the design object
Load applied suddenly or with high velocity.
Cyclic (Repeated) Load
Load that varies with time and is repeatedly applied.
Can lead to fatigue failure, even if stress is below yield strength.
Thermal Load
Caused by temperature changes when expansion or contraction is restrained.
Note: In general, loads are categorized as static, fatigue, or dynamic. For the purpose
of this course, the analysis is limited to static loads.
pg. 2 DBU
College Of Engineering
Department Of Mechanical Engineering
Strength of Materials I
Module
Dejenie W.
Date april/2026
,Strength of Materials I [DATE]
1. Introduction
Branch of mechanics that deals with behavior of materials subjected to various type of
loadings is called Mechanics of solids/mechanics of material or Mechanics of deformable
bodies.
Strength of materials is one branch of mechanics of material;
It deals with the relations between the external forces applied to elastic bodies
and the resulting deformations and stresses.
In the design of structures and machines, the application of the principles of
strength of materials is necessary.
Forces are produced by the action of gravity, by accelerations and impacts of
moving parts, by gasses and fluids under pressure, by the transmission of
mechanical power, etc.
In order to analyze the stresses and deflections of a body, the magnitudes,
directions and points of application of forces acting on the body must be known.
1.1. Types of Loads in Mechanics of Materials
In mechanics of materials, a load is any external force or moment applied to a body that
causes stress, deformation, or failure. Based on how the force acts on the material, loads
are commonly classified as follows:
Axial Load
The Load is applied along the axis of a member. It can be tensile or compressive.
a. Tensile Load
Acts away from the material, trying to stretch it.
Produces tensile stress and elongation.
Common in tie rods, cables, suspension bridges.
b. Compressive Load
Acts towards the material, trying to shorten or crush it.
Produces compressive stress.
Common in columns, pillars, foundations.
pg. 1 DBU
, Strength of Materials I [DATE]
Shear Load
Forces act parallel to the cross-section of the material.
Tends to cause one part of the material to slide over another.
Produces shear stress.
Transverse Load
Applied perpendicular to the longitudinal axis of a member.
Causes the member to bend.
One side experiences tension, the opposite side compression.
Torsional Load
Twisting action caused by a pair of externally applied
equal and oppositely directed couples acting in parallel planes.
Causes the member to twist about its longitudinal axis.
Produces shear stress due to torque.
Distributed Load
Load spread over a length, area, or volume.
Uniformly Distributed Load (UDL) and Uniformly Varying Load (UVL) are
common types of distributed loads.
Impact Load
The impact could be caused by a weight falling on the design object
Load applied suddenly or with high velocity.
Cyclic (Repeated) Load
Load that varies with time and is repeatedly applied.
Can lead to fatigue failure, even if stress is below yield strength.
Thermal Load
Caused by temperature changes when expansion or contraction is restrained.
Note: In general, loads are categorized as static, fatigue, or dynamic. For the purpose
of this course, the analysis is limited to static loads.
pg. 2 DBU
