Name: common wood flaws in lumber
Uploaded: 2024-09-12T16:16:32.000Z
Duration: 1 min 23 s
Channel: JoVE

木材の成長欠陥には、枝が木の幹につながる場所に形成される節、緩い節が脱落することによる節穴、腐敗、虫害などがあります。
揺れは、年輪に沿って、または年輪を横切る小さな亀裂であり、一般的な木材の欠陥です。
ウェインとは、木材が不足しているか、ボードの端に沿って樹皮が存在することを意味します。
チェックとは、丸太に発生する放射状の亀裂のことで、シーズニング工程での円周方向の収縮により発生する製造上の欠陥です。
反りとは、基板内の平らで正確な表面からの偏差を指します。縦糸の種類には、材木の曲がり、お辞儀、ねじれ、カッピングが含まれます。
ハニカムとは、不適切な調味料が原因で発生するボードの内部亀裂を指します。
破れた木目は、切断または平削りによって木材がボードの表面から欠けたりすくい取られたりしたことに起因します。これらの欠陥は木材の強度に影響を与えます。
木材を木材に加工した後、表面の汚れが木材に現れることがあります。これらの茶色、緑、または青の汚れは通常、外観に影響を与えますが、木材の強度には影響しません。

木材の欠陥

Lumber Defects

木材の欠陥は、木材の外観と構造的完全性の両方に影響を与える可能性があり、様々な成長および製造上の欠陥が含まれます。節や節穴などの成長欠陥は、枝がかつて木の幹に付いていた場所に発生し、これらの節が抜け落ちると節穴が形成されます。その他の自然欠陥には、木材の強度と耐久性を損なう腐敗や虫害が含まれます。

シェイクは、木材の年輪に沿ってまたは横切る小さな亀裂であり、一方、ウェインは、木材が欠けたり、板の端に沿って樹皮が存在することで特徴付けられ、通常は木材の切り方に起因します。チェックは、木材内の放射状の亀裂であり、乾燥プロセス中に木材が乾燥して円周方向に収縮するときに現れます。

反りは、木材の平らな表面からの逸脱であり、曲がったり、反ったり、ねじれたり、カップ状になったりして現れ、それぞれが木材の使用性に影響します。ハニカム構造とは、不適切な乾燥によって内部にひび割れが生じることを指し、木材を内部から弱める可能性があります。

木目が裂けることも、切断または削り取りの過程で発生する欠陥の1つです。この段階では木材が欠け、表面が荒れます。最後に、加工後に茶色、緑、青などの表面の汚れが発生することがあります。これらの汚れは通常、木材の外観にのみ影響し、強度には影響しません。

これらの欠陥を理解することは、木材の品質を管理し、木材が建築および製造用途に必要な基準を満たしていることを確認するために重要です。

木材の成長欠陥には、枝が木の幹につながる場所に形成される結び目、緩い結び目が脱落することに起因する節穴、腐敗などがあります。

Education

JoVE Core

Civil Engineering

土木工学

Unit 1

ユニット1

Wood

KEY TERMS AND CONCEPTS

主要用語と概念

common wood flaws in lumber

Lumber defects are flaws in wood that can change both its appearance and its strength. These defects come from tree growth and from the way lumber is processed. Knowing the main defects helps explain why some boards are better for construction and manufacturing than others.

Some defects begin in the tree itself. Knots form where branches were once attached to the trunk, and knotholes appear when those knots fall out. Decay and insect damage are also natural defects that can weaken wood and reduce its durability.

Other defects come from splitting, cutting, or drying the lumber. Shakes are small fractures that run along or across the annual rings. Wane is the missing wood or bark left along a board edge after cutting. Checks are radial cracks that form as wood dries and shrinks during seasoning, and honeycombing is a set of internal cracks caused by improper seasoning.

Warping changes the flat shape of a board. It can show up as crooking, bowing, twisting, or cupping, and each form can make the lumber harder to use. Torn grain is another processing defect, where the wood chips away during cutting or planing and leaves a rough surface. Surface stains, such as brown, green, or blue discoloration, may also appear after processing. These stains usually affect appearance more than strength.

Common Wood Flaws in Lumber

introduction to wood

Wood Structure and Uses in Building

Wood is a construction material made from trees. A tree trunk has several layers. The outside is a protective layer of dead bark. Under that is living bark, then the cambium, then sapwood. As sapwood matures, it becomes heartwood. The pith sits at the center of the trunk. The age of a tree can be read from its growth rings. These rings are concentric bands seen in a trunk cross-section. Wood strength also depends on grain. Grain refers to elongated, tubular cells that run along the length of...

softwoods and hardwoods

Wood Grain in Softwoods and Hardwoods

Softwoods and hardwoods come from different kinds of trees, and their leaf structures and cell makeup help explain how they are used. Softwoods come from cone-bearing trees with needle-like leaves. Hardwoods usually come from trees that shed broad leaves seasonally. Softwoods are made mostly of long cells called tracheids and a smaller number of rays, which are radial cells. This simpler structure gives softwoods a rougher grain. Because of this, they are often used in construction for...

lumber

Lumber Cutting Methods

Lumber is made from logs that are harvested, debarked, and processed into long pieces with a rectangular cross-section. The process starts when an automated saw slices a log into slabs. Those slabs then move on a conveyor belt to smaller saws, where they are cut into square-edged pieces of specific widths. Freshly cut lumber usually has rough surfaces. Its dimensions may also vary slightly from one end to the other. The way wood is cut affects both the lumber’s appearance and how it is used. <br...

structural properties and dimensions of lumber

structural-properties-and-dimensions-of-lumber

Wood Strength Tests and Lumber Sizes

Wood strength depends on how its fibers are aligned along the length of the tree. This alignment gives wood much greater tensile strength along the grain than across it, sometimes up to twenty times higher. Wood also tends to perform better under compression than under tension. Fiber length varies by wood type. Hardwoods have fibers about one twenty-fifth of an inch long. Softwoods have longer fibers that range from one-eighth to one-third of an inch. Laboratory tests help measure how wood...

seasoning of wood

Wood Drying for Stronger Construction

Seasoning of wood is the drying process used to lower and stabilize moisture content before wood is used in construction. Fresh wood can swell when it takes in moisture and contract as it dries. Seasoning helps reduce that movement so the wood stays more stable after it is built into a structure. The main goal is to reach equilibrium moisture content. This is the point where the wood’s moisture level matches the moisture in the surrounding environment. When wood is seasoned properly, it is...

wood surfacing

Wood Surfacing for Smooth, Safe Lumber

Wood surfacing smooths lumber, improves its size accuracy, and makes it safer to handle. It is a key finishing step in woodworking and construction. The process also helps correct small distortions that can form as wood dries. Before surfacing, the wood may be sized slightly larger to account for shrinkage during seasoning, which is the drying stage. A plane, a tool with rotating blades, is used to remove material and smooth the surface. The same tool can also round the edges a little, which...

lumber defects

Lumber defects are flaws in wood that can change both its appearance and its strength. These defects come from tree growth and from the way lumber is processed. Knowing the main defects helps explain why some boards are better for construction and manufacturing than others. Some defects begin in the tree itself. Knots form where branches were once attached to the trunk, and knotholes appear when those knots fall out. Decay and insect damage are also natural defects that can weaken wood and...

wood fasteners

Wood Fastener Types and Uses

Wood fasteners connect parts of a wood structure and help keep members in place. The strength of the connection depends mainly on direct bearing between the wood members. Different fasteners are chosen for different jobs and structural needs. Nails are the most common wood fasteners. They are sharp-pointed metal pins that are driven into wood with a hammer or a mechanical nail gun. Nails come in many diameters, head styles, and lengths. Nailing methods also matter. Face nailing places the...

veneer

How Veneer Is Cut and Used

Veneer is a thin sheet of wood that is usually about one-eighth of an inch thick or less. It is made to show the look of wood while using timber more efficiently. Veneer is common in furniture and other finished wood products. One common way to make veneer is rotary cutting. In this method, a log is mounted in a large lathe and spun against a knife edge. As the knife moves deeper into the turning log, it peels off a continuous strip of wood. This creates rotary-cut veneer. Other veneer...

wood products

Engineered Wood Products in Construction

Engineered wood products are made from wood strands, veneers, lumber, and even waste wood shreds. They are used in both structural and nonstructural building applications. These materials are designed to improve strength, durability, and versatility in modern construction. Glue-laminated wood, or glulam, is made by bonding several smaller pieces of dimensional lumber with adhesive. Cross-laminated timber uses solid lumber panels with layers placed so the grain direction alternates. This layer...

wood panel products

Types of Wood Panels in Construction

Wood panels are common construction materials used for flooring, siding, and roofing. They usually come in standard 4-foot by 8-foot sheets. Their thickness can range from one-quarter of an inch to one and one-eighth inches. Plywood is one of the most familiar wood panels. It is made by gluing thin wood veneers, or layers, under pressure. The outer veneer grain runs lengthwise, while the inner layers run widthwise. Plywood also has an odd number of layers, which helps keep the panel...

key terms and concepts

Learn the main lumber defects found in wood, from knots and decay to warping, checks, and stains, and how they affect strength and appearance.

Common Wood Flaws in Lumber | JoVE K12

JoVE Core Civil Engineering provides a foundational exploration of essential construction materials in civil engineering, focusing on bricks, stones, steel, wood, and concrete through easy-to-understand animated videos. This collection covers the properties, manufacturing processes, and practical applications of these materials. Additionally, the accompanied science-in-action videos demonstrate the research experiments performed in laboratories.

civil engineering

Common Wood Flaws in Lumber

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