Uploaded by Chang.Zhao

fatigue and fracture testing of additive manufactured materials

Fatigue and fracture testing of
additively manufactured materials
Chang Zhao
What is additive manufacturing
Why need tests
What is Mechanical failure
Failure forms of mechanical parts
Causes of mechanical parts failure
Type of test
Test standard
testing machine
What is additive
Additive manufacturing technology,
also known as 3D printing
technology, is a combination of
computer-aided design, material
processing and molding technology.
It is a kind of manufacturing
technology based on digital model,
by using software and control
system, the special materials are
stacked layer by layer according to
extrusion, sintering, melting, UV
curing, spraying, etc., to
manufacture solid parts.
Compared with the traditional processing mode
of raw material removal cutting and assembly, it
is a "bottom-up" manufacturing method through
material accumulation. This makes it possible to
manufacture complex structural parts which
were constrained by traditional manufacturing
methods and could not be realized in the past.
This technology does not need traditional tools,
fixtures and multiple processing procedures. It
can quickly and accurately manufacture any
complex shape parts on one equipment, thus
realizing the "free manufacturing" of parts,
solving the forming of many complex structural
parts, greatly reducing the processing
procedures and shortening the processing cycle.
Moreover, the more complex the product
structure, the more significant the effect of
manufacturing speed.
Why need tests
Mechanical testing is a common
testing used for explore the
mechanical properties of materials.
When using the materials, Material
failure is a very common phenomenon,
and often lead to very bad or even
fatal results. Only when the
mechanical properties are known, the
failure of the material can be avoided
in the process of use. This is the safe
use of materials must know. Thus
analysis in mechanical properties of
applied materials is quite important
and necessary.
What is Mechanical failure
The failure of mechanical parts refers to the partial or complete loss of
design function of parts in the process of use. If the parts are completely
damaged and can not continue to work; or the parts have been seriously
damaged, if they continue to work, they will lose safety; or although they can
work safely, but have lost the design accuracy, they are all failure.
In order to prevent the failure of parts, it is necessary to analyze the failure
of parts, that is, by judging the failure form of parts, determining the failure
mechanism and causes, selecting materials pertinently, determining the
reasonable processing route, and putting forward the measures to prevent
Failure forms of mechanical parts
The common failure forms of mechanical parts can be divided into three types:
excessive deformation failure, fracture failure and surface damage failure.
(1) Excessive deformation failure: Failure of parts due to excessive deformation
exceeding the allowable range. It mainly includes excessive elastic deformation,
plastic deformation and creep under high temperature.
(2) Fracture failure: The phenomenon that parts are separated into two or more
parts which are not connected with each other due to excessive bearing capacity or
fatigue damage. Fracture is the most serious failure mode, which includes ductile
fracture failure, low temperature brittle fracture failure, fatigue fracture failure,
creep fracture failure and environmental fracture failure.
(3) Surface damage failure: The failure caused by surface relative friction or
corrosion by environmental media on the surface of the part caused by damage or size
change. It mainly includes surface wear failure, corrosion failure and surface fatigue
It should be noted that parts often have more than one failure when they are working.
However, there is always a type of failure that plays a leading role.
In this project we focus on excessive deformation failure and fracture failure.
Mechanical failure cases
Causes of mechanical parts failure
There are many and complex factors that cause the failure of mechanical parts, involving the
structural design, material selection, material processing and manufacturing, product assembly,
use and maintenance, etc.
(1) Unreasonable design: It mainly refers to the incorrect or unreasonable structure and shape
of parts, such as the existence of gaps, small arc corners, transition areas of different shapes,
etc. On the other hand, it refers to the insufficient estimation of the working conditions and
overload conditions of the parts, resulting in the insufficient actual working capacity of the
parts, resulting in the early failure of the parts.
(2) Unreasonable material selection: Wrong judgment on the failure form of parts in the
design, the performance of the selected material can not meet the needs of working
conditions; the performance index based on which the material selection is based can not
reflect the resistance of the material to the actual failure form, and the wrong material is
selected; the quality of the selected material is too poor, and the composition or performance
of the material can not meet the design requirements.
(3) Unreasonable processing technology: Improper processing technology of parts may
produce various defects, leading to early failure of parts in the use process. For example,
overheat, overburnt and banded structure appear in hot working process; decarburization,
deformation and cracking appear in heat treatment process; deep tool marks and grinding
cracks appear in cold working process.
(4) Improper installation and use: The assembly and installation process does not meet the
technical requirements, such as too tight, too loose, inaccurate alignment, unstable fixation,
etc., may lead to the parts can not work normally or fail prematurely; in addition, illegal
operation, overload, overspeed, untimely repair and maintenance in the process of use will
also cause premature failure of parts.
Type of test
Bending test:
Bending test is one of the basic methods to measure the mechanical
properties of materials under bending load. In bending test, one side of the
specimen is uniaxial tension, the other side is uniaxial compression. The
maximum normal stress appears on the surface of the sample, which is
sensitive to surface defects. Therefore, bending test is often used to inspect
the surface defects of materials, such as carburizing or surface quenching
layer quality.
Tensile test:
Tensile test is a test method to determine material properties under axial
tensile load. The elastic limit, elongation, elastic modulus, proportional limit,
area reduction, tensile strength, yield point, yield strength and other tensile
properties can be determined by using the data obtained from tensile test.
Test standard
This experiment strictly follows a series of test standards.
ISO 13003:2003 Fibre-reinforced plastics — Determination of fatigue
properties under cyclic loading conditions
ISO 527 Plastics — Determination of tensile properties — Part 1:
General principles
ISO 14125 Fibre-reinforced plastic composites — Determination of
flexural properties
ISO 178 Plastics — Determination of flexural properties
ISO 1268 Fibre-reinforced plastics — Methods of producing test plates
ISO 291 Plastics — Standard atmospheres for conditioning and testing
Standard for specimen preparation
(ISO 527 & ISO 14125)
Create CAD model of specimens
Tensile test
bending test
Testing machine
INSTRON Universal testing machine
All test items in this project
need to be carried out on
Instron universal testing
So far
After determining the project topic, collect relevant literature, discuss the
content to be tested, and select the literature that meets the needs
Literature review
Research proposal
Looking for test standards
Create the CAD model of the specimen meeting the test standard.
Determine some test parameters.
Future plan
The next semester will start to carry out the experiment, because the
experimental variables are numerous and complex, so it will take a long time.
February: Getting ready for the experiment.
March: Start tensile test, including fatigue and failure, test repeatedly to
meet the specified standard, and sort out the data.
April: Start bending test, including fatigue and failure, test repeatedly to
meet the specified standard, and sort out the data.
May: Sort out test data, prepare presentation, write report and PPT.
Thank you
Additive manufacturing equipment
Markforged X7
The software can be quickly
and seamlessly integrated
into the manufacturing
Obtaining industrial-grade
parts in hand in hours, not
weeks — the X7 enables
engineers and designers to
fundamentally improve their
manufacturing operation at
light speed.
Product features
Carbon Fiber Strength
The X7 3D prints Continuous Carbon Fiber reinforced parts in hours that are as
strong as — and capable of replacing — machined aluminum.
Functional Parts of All Types
Whatever your functional requirements are — flame resistant, chemical
resistant, energy absorbent, high resolution, draft parts — the X7 has an
industrial material or print mode capable of fabricating a functional part for
Industrial Reliability and Accuracy
Precision-machined hardware, advanced sensors, and unique software drive
industry leading accuracy and reliability. Only Markforged industrial 3D
printers offer micron-level laser scanning for closed-loop calibration, reliably
yielding parts with 50 μm repeatability and industry-leading surface finish.
What is Eiger
A software suitable for Markforged X7 and dovetails
into workflow
It is basically a digital part repository
It is a simple part library that enables users to
dynamically manage engineering projects of any size —
complete with versioning, permissioning, and
advanced security
It is a powerful prep and print software. Effortlessly
print metal, continuous fiber, and composite base
parts on a single cloud-based interface. features.
Processing mode
Different processing methods also have certain influence on the properties
of the materials. The mechanical properties can be obviously changed by
adding method, quantity, layer number and arrangement position, which
needs many experiments.