PRACTICAL NO.
12
The stress induced in a material depends on the
type of load applied, which can be gradual, sudden,
or impact. Here’s a breakdown of how each load
type affects the material:
1. Gradual Load (Static Load)
Nature: The load is applied slowly and steadily over
time, allowing the material to adjust to the load
without shock.
Stress Induced: The stress is usually uniform,
depending on the cross-sectional area and the
magnitude of the load.
Formula: Stress (σ) = Load (P) / Cross-sectional area
(A).
This type of loading leads to static stress.
Material Behaviour: Under static loads, materials
typically follow Hooke’s Law (within the elastic limit),
which means stress is proportional to strain.
2.Sudden Load (Dynamic Load)
Nature: The load is applied suddenly, but without
significant velocity, often referred to as shock
loading.
Stress Induced: The stress induced in the material is
typically double that caused by a static load of the
same magnitude. This is because the material
doesn’t have time to redistribute or adjust to the load
gradually.
Stress due to sudden load = 2 × Stress due to
gradual load.
Material Behaviour: The sudden application of load
induces higher stresses, and the material must
absorb more energy quickly, increasing the risk of
failure, particularly if the material has low toughness.
2. Impact Load
Nature: The load is applied with a high velocity over
a short duration. This can happen in cases of
collisions, falls, or other high-speed interactions.
Stress Induced: Impact loading induces significantly
higher stress compared to both static and sudden
loads, as the material has to absorb a large amount
of energy in a short time.
The actual stress depends on factors like the velocity
of impact, the mass involved, and the material’s
properties.
Formula: Stress due to impact loading is often
calculated using principles of energy conservation
and dynamics, such as:
½ mv² (kinetic energy of the impacting body).
Σ= mv÷At
(where m is mass, v is velocity, A is cross-
sectional area, and t is time).
